The volunteers were on their way to assess the needs of civilians on the outskirts of Bakhmut, Road to Relief said, in reference to the eastern town that saw the war’s longest and bloodiest battle before falling to Moscow in May.

Associated Press journalists at the site of the attack in the Donetsk region saw covered bodies on the ground and emergency workers extinguishing fires at market stalls, with blackened and mangled cars nearby.

It is in the south that the Ukrainian brigades have made most recent battlefield gains as the counteroffensive inches forward under heavy fire.

The announcement comes as Russia attacked a Ukrainian port on Sunday, a day before key grain deal talks between Russian President Vladimir Putin and Turkey’s president Recep Tayyip Erdogan.

Ukraine’s Air Force spokesman Yuri Ihnat told Ukrainian television on Sunday it wasn’t immediately clear how long the probe would take.

Although Russian officials insisted there was no link between the span and the decision to exit the deal, they described a missile and drone attack on Odesa the day after Moscow broke off the safe shipping agreement as retribution for the damaged bridge.